1. Field of the Invention
The present invention relates to a howling suppressing apparatus.
2. Description of the Related Art
An audio apparatus including a microphone etc. and a speaker etc. forms a feed-back loop when an audio signal output from the speaker travels as a wave to and is input into the microphone. Therefore, howling may be generated depending on the environment for setting up the audio apparatus, the sound volume set for the speaker, positional relationship between the microphone and the speaker etc. To suppress the howling, generally a howling suppressing apparatus is used that detects a frequency band where the howling is generated to suppress the level of the audio signal in the frequency band (e.g., Japanese Patent Application Laid-Open Publication Nos. 7-143034 and 2004-274122). FIG. 11 shows a general howling suppressing apparatus 300. A detecting unit 400 divides an audio signal from a microphone amplifier 310 into a plurality of frequency bands and detects howling in each frequency band. The controlling unit 410 sequentially sets a filter coefficient for suppressing the howling for a plurality of notch filters (NF) 420-1 to 420-n based on the detection result of the detecting unit 400. Therefore, the notch filter 420-n outputs an audio signal with the howling suppressed.
By the way, in the case of an audio apparatus used for karaoke, since the sound volume set for speakers and a position of a microphone relative to the speakers are frequently changed, occurrence condition of howling is accordingly changed and the howling tends to occur for a greater number of times. However, since the howling suppressing apparatus 300 sets a filter coefficient for suppressing the howling for the notch filters 420-1 to 420-n when the howling is detected, it is problematic that the howling cannot be suppressed if the howling is detected for the number of times greater than the number of the notch filters.